I just designed a 8051 mini-computer circuit and I was about ready to do the second side of a double sided board. I discovered at that point when the holes did not match up, that I printed out the transparencies in the wrong orientation. this means that the circuit will not work even if I continued to proceed with it.

so before I make the same mistake again and again of using improper orientation/mirroring, is there any simple steps someone can point out to me that maybe I should be following so that a lightbulb can go off in my head when I print the circuits of both sides out?

I just wasted a $15 circuit board, some etchant, and some developer solution for nothing.

You place text on the top foil side that says "top foil". The bottom foil side should read "bottom". Make sure the text reads correctly with that side of the board up.

I use positive resist coated boards. I print my foil onto transparencies with a laser printer. For double sided boards, I ensure there is an edge with extra transparency material. I match up the vias and through pads and then staple the transparencies along that excess material side.

Careful insertion of the blank PCB between the two transparencies and a bit of clear tape to hold the alignment and I almost always get a good result. If I could just plate the holes, things would be perfect.